Abstract [en]

As part of the Swedish National Eco-steel project, the present work was carried out with a view to study the evaporation of vanadium as V2O5 with a focus on the health hazards. The evaporation rate was followed by monitoring the mass loss from liquid V2O5 melts by thermogravimetric analysis (TGA) in the temperature range 1723 K to 1873 K (1450 A degrees C to 1600 A degrees C). The studies were carried out under three different oxygen partial pressures, viz, oxygen, air, or CO2. The experiments were carried out in the isothermal mode. The Arrhenius activation energies for the evaporation reaction in different atmospheres were calculated from the results. A mathematical model was developed in order to describe the kinetics of the evaporation process. Good agreement could be achieved between the mathematical model and the experimental results. Evaporation coefficients and enthalpies in different atmospheres were also estimated. The present results may also have implications in recovering vanadium values from different vanadium sources.

Yang, Yang

Abstract [en]

Fundamental studies on thermodynamic properties of vanadium-containing oxides systems are essential to understand practical vanadium metallurgical process. The CALPHAD technique is here applied to the thermodynamic modelling of the V-O, Ca-V-O and Ti-V-O systems. The compound energy formalism is used for all the solution phases. All optimization processes and calculations are performed using the Thermo-Calc software package. The present work attempts to develop a self-consistent thermodynamic database of all phases in the studied systems. The obtained datasets can be used to calculate thermodynamic properties, stable as well as metastable phase equilibria and driving forces for oxidation etc.

Steelmaking slag is an important secondary source for vanadium extraction. The phase relationships and vanadium distribution in the CaO-SiO2-MgO-V2O3-Al2O3 synthetic slags, whose compositions were chosen based on the relevance to the steel producers, are also studied. Phase equilibria in the temperature range of 1773 to 1823 K at oxygen partial pressure of 10-10 bar and 0.21 bar were characterized.

An investigation of the volatilization of vanadium oxide was also carried out in the present work. Isothermal evaporation of vanadium pentoxide in the temperature range between 1723 and 1873 K was investigated by Thermogravimetric Analysis under different oxygen partial pressures, viz. oxygen, air or CO2. The Arrhenius activation energy for the evaporation reaction in various atmospheres was calculated from the experimental results. A mathematical model was developed to describe the kinetics of the evaporation process. Evaporation coefficients and enthalpies in various atmospheres were also estimated. The present results may have some implications in recovering vanadium from different vanadium-bearing sources.